1. Field of the Invention
The present invention relates to mountings for carrier bodies in an apparatus for the deposition of semiconductor material on heated carrier bodies and a preferred use of such mountings.
2. The Prior Art
Apparatuses for the deposition of semiconductor material on heated carrier bodies have been known for a long time. For example, see U.S. Pat. No. 4,173,944. In the most common embodiment, such apparatuses comprise essentially a metallic base plate and a coolable bell jar which is placed on the base plate so that a closed reaction chamber is produced in the interior of the bell jar. The deposition apparatus must be capable of being closed in a gas tight and pressure proof manner. This is because the deposition is usually carried out with the application of pressure; and the deposition gases have corrosive action and a tendency to ignite spontaneously when mixed with air. The base plate is provided with mountings upon which the carrier bodies are supported in the reaction chamber. Normally, rods which are heated to the necessary deposition temperature by direct passage of electric current serve as carrier bodies. Expediently, two adjacent rods are connected at their free ends which are opposite to the supported base ends, by a bridge to form a U-shaped carrier body. The electric current is supplied by the pair of mountings supporting the U-shaped carrier body.
A mounting includes a current leadthrough which passes through the base plate and is connected to a current source outside the deposition apparatus. Inside the deposition apparatus, the current leadthrough is constructed as an electrode holder or is permanently connected to a separate electrode holder. Mounted on the electrode holder is a graphite electrode which is directed into the reaction chamber. The graphite electrode normally has a recess at the top into which the carrier body is inserted. The mountings are designed so that the supported carrier bodies are fixed in position and cannot be moved. The current leadthrough and, if applicable, also the electrode holder are provided with a cooling channel through which a coolant is pumped during the deposition. This prevents semiconductor material from depositing on the mounting of the carrier body.
Since the development of the first deposition apparatuses, there has been a continuous tendency to produce semiconductor bodies with ever larger volumes by depositing semiconductor material on heated carrier bodies. At present, semiconductor rods whose length is up to 3000 mm and whose diameter is up to 200 mm are produced using rod-shaped carrier bodies. In the production of large semiconductor bodies, it can be observed relatively frequently that, in the final stage of the deposition or during the cooling phase after the deposition they are damaged by cracks. This phenomenon causes a high financial loss since damaged semiconductor bodies can no longer be further processed as planned.